<!-- Licensed under a BSD license. See license.html for license -->
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes">
<title>WebGL2 - Planar Projection - Setup</title>
<link type="text/css" href="resources/webgl-tutorials.css" rel="stylesheet" />
</head>
<body>
<div class="description">
Planar Projection - Setup
</div>
  <canvas id="canvas"></canvas>
  <div id="uiContainer">
    <div id="ui">
    </div>
  </div>
</body>
<!--
This sample uses TWGL (Tiny WebGL) to hide the clutter.
Otherwise the sample would be full of code not related to the point of the sample.
For more info see https://webgl2fundamentals.org/webgl/lessons/webgl-less-code-more-fun.html
-->
<script src="resources/webgl-lessons-ui.js"></script>
<script src="resources/twgl-full.min.js"></script>
<script src="resources/m4.js"></script>
<script>
'use strict';

const vs = `#version 300 es
in vec4 a_position;
in vec2 a_texcoord;

uniform mat4 u_projection;
uniform mat4 u_view;
uniform mat4 u_world;

out vec2 v_texcoord;

void main() {
  // Multiply the position by the matrix.
  gl_Position = u_projection * u_view * u_world * a_position;

  // Pass the texture coord to the fragment shader.
  v_texcoord = a_texcoord;
}
`;

const fs = `#version 300 es
precision highp float;

// Passed in from the vertex shader.
in vec2 v_texcoord;

uniform vec4 u_colorMult;
uniform sampler2D u_texture;

out vec4 outColor;

void main() {
  outColor = texture(u_texture, v_texcoord) * u_colorMult;
}
`;

function main() {
  // Get A WebGL context
  /** @type {HTMLCanvasElement} */
  const canvas = document.querySelector('#canvas');
  const gl = canvas.getContext('webgl2');
  if (!gl) {
    return;
  }

  // setup GLSL programs
  const textureProgramInfo = twgl.createProgramInfo(gl, [vs, fs]);

  // Tell the twgl to match position with a_position,
  // normal with a_normal etc..
  twgl.setAttributePrefix("a_");

  const sphereBufferInfo = twgl.primitives.createSphereBufferInfo(
      gl,
      1,  // radius
      12, // subdivisions around
      6,  // subdivisions down
  );
  const sphereVAO = twgl.createVAOFromBufferInfo(
      gl, textureProgramInfo, sphereBufferInfo);
  const planeBufferInfo = twgl.primitives.createPlaneBufferInfo(
      gl,
      20,  // width
      20,  // height
      1,   // subdivisions across
      1,   // subdivisions down
  );
  const planeVAO = twgl.createVAOFromBufferInfo(
      gl, textureProgramInfo, planeBufferInfo);

  // make a 8x8 checkerboard texture
  const checkerboardTexture = gl.createTexture();
  gl.bindTexture(gl.TEXTURE_2D, checkerboardTexture);
  gl.texImage2D(
      gl.TEXTURE_2D,
      0,                // mip level
      gl.LUMINANCE,     // internal format
      8,                // width
      8,                // height
      0,                // border
      gl.LUMINANCE,     // format
      gl.UNSIGNED_BYTE, // type
      new Uint8Array([  // data
        0xFF, 0xCC, 0xFF, 0xCC, 0xFF, 0xCC, 0xFF, 0xCC,
        0xCC, 0xFF, 0xCC, 0xFF, 0xCC, 0xFF, 0xCC, 0xFF,
        0xFF, 0xCC, 0xFF, 0xCC, 0xFF, 0xCC, 0xFF, 0xCC,
        0xCC, 0xFF, 0xCC, 0xFF, 0xCC, 0xFF, 0xCC, 0xFF,
        0xFF, 0xCC, 0xFF, 0xCC, 0xFF, 0xCC, 0xFF, 0xCC,
        0xCC, 0xFF, 0xCC, 0xFF, 0xCC, 0xFF, 0xCC, 0xFF,
        0xFF, 0xCC, 0xFF, 0xCC, 0xFF, 0xCC, 0xFF, 0xCC,
        0xCC, 0xFF, 0xCC, 0xFF, 0xCC, 0xFF, 0xCC, 0xFF,
      ]));
  gl.generateMipmap(gl.TEXTURE_2D);
  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);

  function degToRad(d) {
    return d * Math.PI / 180;
  }

  const settings = {
    cameraX: 2.75,
    cameraY: 5,
  };
  webglLessonsUI.setupUI(document.querySelector('#ui'), settings, [
    { type: 'slider',   key: 'cameraX',    min: -10, max: 10, change: render, precision: 2, step: 0.001, },
    { type: 'slider',   key: 'cameraY',    min:   1, max: 20, change: render, precision: 2, step: 0.001, },
  ]);

  const fieldOfViewRadians = degToRad(60);

  // Uniforms for each object.
  const planeUniforms = {
    u_colorMult: [0.5, 0.5, 1, 1],  // lightblue
    u_texture: checkerboardTexture,
    u_world: m4.translation(0, 0, 0),
  };
  const sphereUniforms = {
    u_colorMult: [1, 0.5, 0.5, 1],  // pink
    u_texture: checkerboardTexture,
    u_world: m4.translation(2, 3, 4),
  };

  function drawScene(projectionMatrix, cameraMatrix) {
    // Make a view matrix from the camera matrix.
    const viewMatrix = m4.inverse(cameraMatrix);

    gl.useProgram(textureProgramInfo.program);

    // Set the uniform that both the sphere and the plane share
    twgl.setUniforms(textureProgramInfo, {
      u_view: viewMatrix,
      u_projection: projectionMatrix,
    });

    // ------ Draw the sphere --------

    // Setup all the needed attributes.
    gl.bindVertexArray(sphereVAO);

    // Set the uniforms unique to the sphere
    twgl.setUniforms(textureProgramInfo, sphereUniforms);

    // calls gl.drawArrays or gl.drawElements
    twgl.drawBufferInfo(gl, sphereBufferInfo);

    // ------ Draw the plane --------

    // Setup all the needed attributes.
    gl.bindVertexArray(planeVAO);

    // Set the uniforms unique to the plane
    twgl.setUniforms(textureProgramInfo, planeUniforms);

    // calls gl.drawArrays or gl.drawElements
    twgl.drawBufferInfo(gl, planeBufferInfo);
  }

  function render() {
    twgl.resizeCanvasToDisplaySize(gl.canvas);

    // Tell WebGL how to convert from clip space to pixels
    gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);

    gl.enable(gl.CULL_FACE);
    gl.enable(gl.DEPTH_TEST);

    // Clear the canvas AND the depth buffer.
    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

    // Compute the projection matrix
    const aspect = gl.canvas.clientWidth / gl.canvas.clientHeight;
    const projectionMatrix =
        m4.perspective(fieldOfViewRadians, aspect, 1, 2000);

    // Compute the camera's matrix using look at.
    const cameraPosition = [settings.cameraX, settings.cameraY, 7];
    const target = [0, 0, 0];
    const up = [0, 1, 0];
    const cameraMatrix = m4.lookAt(cameraPosition, target, up);

    drawScene(projectionMatrix, cameraMatrix);
  }
  render();
}

main();
</script>
</html>



